Martin J. Hayes

A comparative review of wireless sensor network mote technologies

In the past 10 years, wireless sensor networks have grown from a theoretical concept to a burgeoning modern technology. In this paper, we present a comparative review of several wireless sensor network motes. We analyze these WSN devices under a number of different parameters and criteria, including processing ability, expected lifetime and measurement capabilities. We compare and contrast the selected WSN motes under these different headings, highlighting the individual motes performance under each category

New Tools for Computing Tight Bounds on the Real Structured Singular Value

New tools are presented for the computation of tight lower bounds on the structured singular value π, for highorder plants subject to purely real parametric uncertainty. The e rst approach uses the π-sensitivity function to systematically reduce the order of the real uncertainty matrix, so that exponential time lower bound algorithms can be applied. The second approach formulates the search for a worst-case real destabilizing perturbation as a constrained nonlinearoptimization problem.Both approachesareapplied to theproblem ofanalyzing thestability robustness properties of an integrated e ight and propulsion control system for an experimental vertical/short takeoff and landing aircraft cone guration. Currently available software tools for calculating lower bounds on real π fail for this problem, whereas both new approaches deliver tight bounds over the frequency range of interest.

Green’s function for steady flow over a small two-dimensional topography

We consider steady flow of a thin viscous liquid film over a small two-dimensional topography and develop a Green’s function for the linearized problem. The solutions so obtained can be used to analyze the effect of arbitrary small substrate defects on the coating applied to a substrate.

Robust active queue management design: A loop-shaping approach

In this paper, a novel systematic design procedure is presented for robust active queue management (AQM). The congestion control law is obtained through an interactive loop-shaping process that manipulates the system frequency response to meet robust stability and performance requirements in the presence of uncertain network conditions. A sufficient condition leading to a satisfactory level of robust performance against high-frequency parasitics that naturally affect the desired requirements is then derived. A feature of the technique is that the uncertain phase information and round-trip time-delay that are inherent to the system dynamics are fully addressed in the design equations, resulting in minimal conservatism and/or over-design. Simulation results using the ns2 simulator are provided to illustrate the effectiveness of the proposed method.

Robust performance for an energy sensitive wireless body area network – an anti-windup approach

This paper applies a robust anti-windup (AW) based control scheme to optimise throughput rate for an 802.15.4 wireless body area network (WBAN) that is subject to naturally occurring input saturation constraints. The technique uses an intuitively appealing two step design procedure. Firstly, a robust H∞ loop-shaping linear controller is designed providing nominal (un-saturated) robust performance. Then Weston–Postlethwaite AW compensation techniques are used to minimise the adverse effects of any control input non-linearities on closed loop performance. The methodology provides guaranteed quality of service (in this context taken to mean that sufficient data is always available to reassemble the required biometric waveforms, e.g. ECG) while concurrently minimising power consumption over an extended usage period. This joint robust performance question is validated on an experimental mote based 802.15.4 wireless sensor network.

Robustness analysis of an integrated flight and propulsion control system using μ and the ν-gap metric

Abstract This paper describes the application of two frequency domain analysis tools, the structured singular value μ and the ν -gap metric, to the problem of evaluating the robustness properties of a multivariable integrated flight and propulsion control (IFPC) system for an experimental V/STOL aircraft configuration. Variations in aircraft parameters and dynamics over the V/STOL flight envelope are represented as linear fractional transformation (LFT) based parametric uncertainty descriptions, using a simple ‘black-box’ type modelling approach. Tight bounds on μ for the resulting high-order real parametric uncertainty model are computed by introducing small amounts of additional complex uncertainty, in order to analyse the stability robustness properties of the IFPC system. Stability and performance robustness of the IFPC system is also evaluated using the ν -gap metric. Results generated by both analysis tools are seen to be consistent, and to agree well with evaluation results obtained for the IFPC system in piloted simulation.

On the effect of communication constraints on robust performance for a practical 802.15.4 wireless sensor network benchmark problem

This work considers the effect of communication constraints on the dynamic performance of wireless sensor networks that operate in a power aware mode. In particular, the hardware output power limit and quantization constraints that arise practically when only a limited number of power levels are available to the designer are considered in this regard. A novel approach is presented that uses an intuitively appealing graphical means of representing an output power constraint, whereby the saturation block that naturally occurs in a practical setting is mapped from the output of the plant and is compensated through the use of a robust Anti-Windup scheme. System performance and stability is verified using quantitative feedback theory in the linear part of the design. The hybrid controller that ensues is extensively tested experimentally, on a fully compliant 802.15.4 testbed, where mobility is considered in the problem formulation using a team of fully autonomous robots. A benchmark comparison is made between this approach and a number of existing strategies suggesting that an anti-windup approach is an entirely appropriate methodology for the problem at hand.

A Robust Throughput Rate Control Mechanism for an 802.15.4 Wireless Sensor Network - An Anti-Windup Approach

This paper presents a novel throughput rate control mechanism for an 802.15.4 wireless sensor network. Power consumption within the network is regulated using anti-windup techniques thereby minimising power loss while simultaneously preserving quality of service (QoS). A full order anti-windup scheme has been designed and tested experimentally on the network. The scheme exhibits good command tracking, disturbance rejection and increased battery life.

Robust Active Queue Management using a Quantitative Feedback Theory Based Loop-Shaping Framework

In this paper an alternative robust control design based on Quantitative Feedback Theory (QFT) is presented for Active Queue Management (AQM) routers supporting Transmission Control Protocol (TCP) flows. At first, it is shown how the problem can be presented in the QFT loop-shaping framework and then the robustness requirements are formulated based on the nature of the system. A sufficient condition for obtaining a satisfactory level of robust performance against high-frequency parasitics is introduced. Experimental results using the ns simulator are provided to illustrate the effectiveness of the proposed method.

Control for a Variable Speed Wind Turbine Equipped with a Permanent Magnet Synchronous Generator (PMSG)

In wind turbine systems, one of the operational problems is the unpredictable factor of wind. This leads the quality of produced energy becomes an important problem in the system. Several control techniques have been applied to improve the quality of power generated from wind turbines. Pitch control is the most efficient and popular power control method, especially for variable-speed wind turbines. In this paper, a traditional PI controller is developed. Simulations were carried out to validate the proposed control design when realistic data of wind speed collected in Borj Cedria, Tunissia, are taken into account.